Bio-remediation is an increasingly popular approach for treatment of soils such as silt, clay, crushed porous type rock, and the like that has been contaminated with organic compounds. For example, bio-remediation has been employed in the treatment of subsurface soils contaminated by hydrocarbons as in the case of leaking underground tanks, pits or pipes. Bio-remediation has also been used in the treatment of water-borne oil and gas contamination such as in tanker mishaps, soil accumulated on drilling platforms, pipeline leaks and the like.
While the utilization of bacterial microorganisms for remediation has enjoyed some success, there are problems with implementation of various bio-remediation methods that have been proposed. A particular problem is that bio-remediation methods tend to be somewhat inefficient and time-consuming and require treatment of contaminated soil in relatively small batches. The treatment of such contaminated soil has been actively featured in recently issued patents. Note for example, U.S. Pat. No. 5,039,415 to Smith, and U.S. Pat. No. 4,849,360 to Norris. The apparatuses heretofore employed for such soil decontamination generally have a limited treatment capacity measured in terms of less than 50 cubic yards of contaminated soil per batch. Weeks or months are often required for the microbes to bio-remediate the soil, particularly when the ambient temperature falls below 0.degree. F. Where large quantities of contaminated soil exist, it has been disclosed in U.S. Pat. No. 5,178,491 to Graves, et al. to dig a trench in the vicinity of the contaminated soil or to install a concrete bunker and treat large quantities of soil in such structures. Such trenches and bunkers are of a permanent nature, costly to produce and can only be utilized for treatment of contaminated soil located within a reasonable transport distance.
A problem that is common to a broad range of industries is soil areas that have been contaminated with diesel, gasoline, lubricating oils, and various other petroleum hydrocarbons used in vehicle operation or in maintenance procedures. Those hydrocarbon contaminated areas are typically found in maintenance yards, equipment cleaning areas, fuel and lubricant storage areas, refueling areas, and around tank terminal operations. Often those areas cannot be closed while the soil is excavated, removed to another location, treated, and then replaced in the same location. The present invention does not require the closure of the contaminated area to bio-remediate the contaminated soil areas.
Historically, the common tendency of industry has been largely to ignore these contaminated areas and just accept them as a part of normal operations. However, with the advent of a much greater level of environmental awareness by the public and pressures coming to bear from regulatory authorities, such as the Environmental Protection Agency, many industries are beginning to search for an economic, efficient method of addressing this problem.
A number of alternatives are available for handling hydrocarbon contaminated soils. The traditional solution has been to dig up the contaminated soil and send it to a waste disposal firm. This solution tends to be relatively expensive. The cost to handle the contaminated soils ranges from $200 up to $1,000 per yard of soil depending upon the area of the country in which the disposal is being done.
As an alternative to these traditional approaches, a new technology has emerged to address this problem. This technology is the cleanup of the soil on site using a balanced bio-remediation approach. The balanced approach involves excavating the contaminated soil and biologically, chemical, thermally, and mechanically treating the soil. The final step in the balanced approach is returning the once contaminated soil to its place of origin containing natural nutrients capable of starting and sustaining vegetation. In fact, contaminated soil processed by the present invention, utilizing a balanced approach may be removed from the contamination site, remediated, then deposited in a third site that requires uncontaminated soil.
Most soil and water contain significant populations of microscopic one celled organisms that have the capacity to break down and decompose plant and animal waste. Functionally, these microscopic organisms utilize the waste organic compound as a food source and degrade the organic compound to create carbon dioxide, water, fatty acids, and cell mass. It is by this process that leaves, dead vegetation, and other organic materials are converted into humus that makes up the organic portion of the soil. There are also many natural organisms that have the ability to utilize diesel-fuel, kerosene, gasoline lubricating oils, and other petroleum hydrocarbons as a food source. There are also organisms which are specifically genetically engineered to be able to use such petroleum hydrocarbons as a food source, thus breaking these hydrocarbons down into smaller components which are more easily digested by indigenous natural organisms already existing in the soil. However, microbes are only part of the solution to bio-remediation of contaminated areas. The breaking apart and emulsifying the soil is necessary for providing a vehicle for the microbes to reach the emulsified soil to begin the remediation process.
Accordingly, the present invention is a balanced system to remediate contaminated soil and recover hydrocarbons that is economical, time efficient, portable and easy to implement. The total balanced approach to remediating soil is uniquely intra-woven into the method and apparatus of the claimed invention.